Knife grinding machine



March 1957 B. J. R. JANSSON 2,786,310

KNIFE GRINDING MACHINE 3 Sheets-Sheet 1 Filed Nov. 1'7, 1953 6 INVENTOR. 50h: [Ms Jam/v foals-er Jwssoxv 35 y 7% wfi izguw March 26, 1957 B. J. R. JANSSON 2,785,310

KNIFE GRINDING MACHINE Filed Nov. 17, 1953 3 Sheets-Sheet 2 I I INVENTOR. 50%! 1425 (/w/LM/ fast-er (/zwasa/v March 26, 1957 B. L. J. R. JANSSON KNIFE GRINDING MACHINE 3 Sheets-Sheet 3 Filed Nov. 1'7, 1953 INVENTOR flaeaz/Ms Jew/w fafizer w/vsso/v "lllllllllllllllllllllllllllllHllllllljjjllljb ATTORNEYS United States Patent KNIFE GRINDING MACHINE Brge Lars Johan Robert Jansson, Copenhagen, Denmark,

assignor to Carl Norman Kuehn, Copenhagen, Denmark Application November 17, 1953, Serial No. 392,663

Claims priority, application Sweden November 18, 1952 Claims. (Cl. 51-98) This invention relates to a cutting tool, more particularly a table knife with a curved edge, along which are ground a series of recesses in the blade of the knife.

Most knives used in the household, particularly table knives, are liable to become dull very soon since they get into contact with porcelain when used whereby the edge of the knives is spoilt by the hardness of the porcelain. This applies both to ordinary smooth knives and knives of the said designs. Since household knives are usually made of stainless steel which has little resistance to the said kind of wear this means a great disadvantage, and if household knives and particularly table knives are to have a certain cutting capacity, they have to be ground frequently.

It is the object of the invention to provide a knife of such a design that its edge can be kept sharp for a longer time than the known knives, even though used on porcelain. This is achieved by virtue of the fact that the recesses, which are provided on one side only of the blade, are placed directly beside each other in such manner that, viewed from the side, the edge takes the form of a corrugated line with small flat arches intersecting each other at projecting points along the edge of the knife, the said recesses having a crescent-formed cutting edge, no material having been ground away at the projecting points.

When such a knife is used on porcelain, only the projecting points will be in contact with the porcelain surface, and these points which have not been weakened by the grinding will therefore last longer. In contrast to this the deeper parts of the cutting edge, constituted by the points where the bottom of the recesses meet the opposite side of the blade, will not at all get into contact with the porcelain, and so the sharpness will be preserved.

The recesses are conveniently made in such manner that the arches in the corrugated line are rather flat, so that the cutting edge does not deviate very much from the even shape. This feature in combination with the fact that only one side of the blade has recesses makes it possible to use the knife for buttering without leaving deep grooves in the buttered surface.

The present invention is also concerned with a grinding machine for grinding cutting tools of the aforesaid kind.

If the object solely consisted in providing a number of ground places in a blank having a rectilinear edge, the structural design of a suitable machine would be comparatively easy. However, grinding of cutting tools with a curved cutting edge entails certain difficulties which render the solution of the problem considerably more complicated. Table knives never have a rectilinear cutting edge; on the contrary, the said edge is more or less curved so that, especially near the point of the blade, there may be a rather round curve. Furthermore it is desirable that the machine is adapted in such manner that proper grinding does not require very accurate positioning of the knives in the machine.

It is the object of the invention to provide a grinding 2,786,310 Patented Mar. 26, 1957 machine adapted in such manner that it is capable of performing the aforesaid operation even though the cutting edge of the knife curves to a considerable degree and even though the cutting tool is set up by eye-measurement. A

characteristic feature of the machine according to the invention is that it has a rotating grinding wheel with a curved profile and a table for mounting the knife in such a position that its cutting edge is substantially parallel with the axis of rotation of the grinding wheel. In addition, the said machine is provided with a feed mechanism to provide a stepwise combined, relative movement between the table and the grinding wheel, each stepwise movement consisting of a movement in the direction of the cutting edge followed by a movement in the transverse direction of the first mentioned direction, in which the grinding wheel and the knife are approached to eachother and finally a transverse movement in the opposite direction in which the grinding wheel and the knife areremoved from each other. The said feed mechanism comprises an idling member adapted to permit discontinuance of the first mentioned movement before it has reached the extreme point determined by the components of the said mechanism without the mechanism stopping for this reason, and an adjustable stop member whose position in relation to the axis of rotation of the grinding wheel remains unaltered during the grinding operation,

- the said stop member being placed in such manner that on the first mentioned transverse movement it will be intercepted by the edge of the knife directly beside the grinding wheel.

Further features and characteristics of the machine according to the invention will be disclosed in the following description and the claims. 7

An embodiment of a machine in accordance with the invention will now be described with reference to the drawing, in whichr Figure 1 shows a machine, viewed in perspective, having part of its carriage or slide cut away so as to permit the components lying behind to be seen.

Figure 2 shows a block for moving the cross slide, viewed from above. I

Figure 3 is a section on the line IIIIII of Figure 2.

Figure 4 is a section of a stock for mounting a stop member, and

Figure 5 is a section on the line V--V of Figure 4.

Figure 6 shows a part of a knife, and

Figure 7 shows the knife, viewed from the opposite side.

Figure 8 is a fragmentary side elevation of an exemplary gearing mechanism which may be employed as the intermittent feed mechanism of the present invention, and

more drives a shaft 9 which through a worm gearing 10 drives a transverse shaft 11. The end of the shaft 11 is provided with a coupling half 12. cooperating with another coupling half on a shaft 13. The coupling may be engaged or disengaged by means of a hand lever 14.

The shaft 13 drives a wheel gearing denoted as a whole by 15, and from which a spindle 16 and a shaft 17, both parallel to the axis of rotation of the grindingwheel 4, are driven. The frame 1 has slideways 18 supporting a slide or carriage 19 capable .of moving in a direction which is parallel to the axis of rotation of the grinding Wheel, and the movement may be automatic by means of the spindle 16. The slide 19 has a slide- Way 20 a right angle to the slideways 1.8, and he said slideway 2.0 supports a transverse slide or carriage 21 which is provided with fixing m mbers consis ng f a fixing pla e 2.2 and a handle .2 i h an ecc ntric disc 24 y means of which a knife 5 may be ed int P0- sition on the transverse slide .21 so that the edge of the knife is substantially parallel to the axis of ro on of the grinding Wheel.

On the underside of the transverse slide 21 there is attached a block 26 received in a cavity in the slide 19. The block 26 is attached to the transverse slide 21 by means of screws received in threaded holes 27 in the block.

The block 26 is illustrated on an enlarged scale in Figures 2 and. 3. As will be seen from these figures, the blockv is provided with a through-going square hole 28 and a transverse oblong hole 29 through which the shaft 17 extends, The block is furthermore provided with a hole 30 at right angles to the hole 29, The rear end of the said hole 0 has a screw thread 31 in which there is scr wed a h lding member 32 constit t ng an adjustable rest for a heli al sp ing .33, the o her end of which is received in a. hole in a op pin 34 whose hemipheric l end is pres ed gain t 21 e rn 35 y the Spring 33.. The sai cam .35 is a tached o the shaft 17.

Beside. the grind ng wheel 4 h frame 1 carries a stock 36 with a groove 37 (Figure 4), in which a bar 38 serving as stop is fixed by means of two screws 39. The Said stock is furthermore provided with an adjust ment screw by means of which the stop 38 can be finely adjusted in axial direction. As will be evident from Figure 5, one end of the stop is pointed, i. e. the end directly beside the peripheral .part of the grinding wheel 4 which isslightly curved.

The machine operates as follows:

The knife 25 which is assumed to have a smooth cutting edge is'zmounted in such position on the slide 21 that its edge is substantially parallel to the direction of movement of the slide 1.9., and the knife is fixed by means of the members 22, 23 and 24. The stop '38 is adjusted in such manner in relation to the periphery of the grinding wheel that the wheel, as illustrated in Figure 5, may produce the desired arched or curved form of the cutting edge before the stop 38 by contacting the said edge prevents further approach between the knife and the grinding wheel. When the electric motor .is started, the grinding wheel 4 begins rotating, and as soon as the shafts 13 and 11 are coupled together by means of the hand lever 14 the spindle 16 .and the shaft 17 will be driven in special manner by means of the Wheel gearing 15. The wheel gearing is adapted in such manner that a rotating movement is first imparted to the spindle .16 wh r by the sl de .1 m ve forward along a distance corresponding to a wavelength of the edge of the knife, after which the spindle -16 is stopped, whereas the shaft 17 makes a r olu i n- Du ing this movement the cam 35 will carry the block 26 and consequently the transverse slide 21 in ,towards the ng Wheel and back again, th spring 3 en uring that the stop pin 34 is constantly resting against surface of the cam. When the transverse slide 21 has performed the movement just described, the spindle 16 is again moved, so that the slide '19 is moved one step forward. The slide 19 will then stop, whereas the trans verse slide 21 again performs a transverse movement.

By the transverse movement of the transverse slide 2,11the knife is carried towards the grinding wheel which grinds a :curved recess in the cutting edge as shown in Figure 5. The movement is discontinued when the edge ofdhe :knife is intercepted by the stop 38, and this'wi-ll occur Ehetore the highest point of the cam 35 has reached the stop pin 34. The cam 35, however, continues its movement, and the pin 34 is pressed further back without the block 26 and, consequently, the transverse slide 21 partaking of this movement, the further movement being absorbed by the spring 33 which is compressed. The spring 33 is so rigid that it will not be compressed to any extent worth mentioning as long as the movement of the slide 21 is not stopped by the stop 38. Return of the slide 21 away from the grinding wheel 4 is produced by the tail of the cam 35 bearing against the'end wall of the opening 28 in the block 26 disposed opposite the stop pin 34. l

Figures 8 and 9 of the drawing illustrate a gearing mechanism which may be employed for the gearing 15 to produce the alternate stepping of the carriage 19 and slide 21. As illustrated in Figtltcs 8 and 9, a worm gear 4-1 may be aifixed to the end of the shaft 13, which worm gear 41 engages a worm gear 42 on the shaft 17, whereby the shaft 17 will be rotated continuously with the shaft 13. A stub shaft .43 may be fixed on the frame 1 and provided with a gear 44 journaled on the shaft 413, which engages .a gear .45 on the spindle 16 and a gear 455 on the shaft 17. The gears 45 and 46 therefore rotate in the same direct-ion when the shaft 13 rotates.-

Some of the teeth are omitted from the gear 46 so that rotation is imparted to the gear 44 only when the remaining teeth of the gear 46 are in engagement with the teeth on the gear .44. Therefore, only intermittent rotation is imparted to the gears 44 and 45 from the gear 46,.

There may be fixed to the gear 46 a disk 47 having a cam 48 thereon, and a disk 49 having two cams 50 may be fixed to the gear 44. The cams 50 have outer surfaces which are curved complementary to the periphery of the disk 47 so that the .cams 5'0 serve as stop members, preventing the gear 544 from rotating when the. teeth of the gear 4.4 are not in engagement with the teeth of the gear 46. When the cam 4.8 engages the 6 m 50, the remaining teeth on the gear 416 engage the teeth on the gear 4.4 so that the cam 50 serves to prevent incorrect engagement between :the teeth of these gears. When the cam .48 engages the cam 50, and the teeth of gears 44 and 46 are in engagement, the gear 44 is rotated and the cam 50 is moved out of the path of the earn .48. By this movement, therefore, continuous rotation is imparted to the shaft '17 which, due -to the surface of the cam 35 imparts only intermittent reciprocatory movement to the slide .21, and only intermittent rotation is imparted ,to the screw threaded spindle 16 to advance :the carriage 19 parallel to the axis of rotation of the grinding wheel 4.

1t will be evident from the foregoing description that the grinding wheel 4 will always make cuts .of uniform depths in the knife, irrespective of the cnrvature of the blade, the .rnovement being solely determined 'bytthe stop which is intercepted :by the edge of the knife directly beside the grinding wheel. It will therefore be possible to out or grind a cutting edge .of accurate corrugations. ir espective of the degree .of curvature .of the knife, or whether the knife is fixed in uneven position in relation to the direction of movement of the slide 19. As the. position of the grinding wheel in relation .to the knife remains unaltered during the grindingoperation, the curved grindings of the cutting edge will be .of a slightly different shape ,at the points where the cutting edge of the ,lgnifeis very rnuch curved, for example, at the pointed end of the knife, :but :this has been found to be .unessential, and when fixing the knife in-the machine regard may be taken :to these conditions by fixing the knife, as far as possible, in such manner that its "degree of curvature is uniform on either side of the direction of movement.

In the case of knives having a very pronounced curv ture it may be necessary toiperform the grinding opera,- tion in two or more stages.

-On -re-grindingkniveshaving already a corrugated cutting edge, the knife is placed in such manner that one of the corrugations is in contact with the curved surface of the grinding wheel when stationary, and in such manner that the curvature of the knife as previously described is uniform on either side of the direction of movement. The grinding operation may then take place in the same easy manner as in the case of a knife with rectilinear edge, the stop 38, which will be intercepted by the projecting points of the knife edge, ensuring that the grinding wheel penetrates to equal depths of the various recesses.

Figures 6 and 7 show a part of a table knife ground according to the invention. One side of it (Figure 6) has a plurality of recesses ground as shown in Figure 5, so that the edge of the knife is slightly touched, whereby a corrugated line has been produced with a plurality of slight corrugations as indicated in Figure 7. The recesses have a crescent-like cut which does not contact the projecting points, whereby the material at these is left unweakened. Owing to this the edge as a whole retains its strength despite a very sharp cutting edge in the recesses.

What I claim and desire to secure by Letters Patent is:

1. A grinding mechanism for grinding a series of armate concave depressions in the cutting edge of an elongated flat sided blade of a knife and the like comprising a frame, a driven rotary grinding wheel on said frame having a peripheral grinding edge of arcuate convex crosssection, table means having clamping means thereon for supporting a knife adjacent said grinding edge with the cutting edge of the knife arranged parallel to the axis of rotation of said grinding Wheel, carriage means having guide means thereon slidably supporting said table for reciprocative rectilinear movement perpendicular to said axis of rotation, guide means on said frame supporting said carriage for rectilinear movement parallel to said axis of rotation, a feed mechanism including longitudinal feed means for shifting said carriage means with said table means thereon in discrete steps in a direction parallel to said axis of rotation and transverse feed means for reciprocating said table means rectilinearly toward and then away from said grinding edge, said longitudinal feed means and transverse feed means being operable in alternation whereby said table means is shifted to advance a knife supported thereon in the direction ofits cutting edge a distance substantially equal to the Width of said grinding edge and then approach the cutting edge of the knife into contact with said grinding edge and withdraw the same therefrom, adjustable stop means positioned on said frame adjacent said grinding wheel to abut the cutting edge of the knife when the same has approached said grinding edge to an extent to effect grinding of a preselected depth of cut, and resilient means incorporated in said transverse feed mechanism terminating approaching movement of said table means and knife cutting edge when said cutting edge abuts said adjustable stop means.

2. In a grinding machine for grinding a series of arcuate concave depressions in the cutting edge of an elongated flat sided blade of a knife or the like, the combination recited in claim 1 wherein said transverse feed means comprises a driven shaft disposed parallel to said grinding wheel axis having a cam thereon disposed in parallelism with the plane of said grinding wheel, and cam follower means depending from said table means into juxtaposition with diametrically opposite faces of said cam to be engaged by said cam for imparting reciprocative approaching and withdrawing movement to said table means relative to said grinding edge, said cam follower means including resilient lost motion means engaged by said cam during approaching movement of said table to terminate transfer of grinding-wheel-approaching movement from said cam to said table means when said cutting edge abuts said stop means.

3. In a grinding machine for grinding a series of arcuate concave depressions in the cutting edge of an elongated flat sided blade of a knife or the like, the combination recited in claim 1 wherein said carriage means comprises a centrally open frame underlying said table means, and said transverse feed means comprises a driven shaft underlying said carriage means and disposed parallel to said grinding wheel axis having a cam thereon disposed in parallelism with the plane of said grinding wheel, a block depending from said table means through said carriage means opening into encompassing relation with said cam having an opening therein for the reception of said cam and slots receiving said shaft for accommodating reciprocal movements of said block perpendicular to the axis of said shaft, said block having a resilient lost motion cam follower projecting into said block opening for contacting the surface of said cam for shifting said table means to approach said grinding edge and a fixed cam follower surface juxtaposed to a diametrically opposite surface of said cam to be engaged by said cam for withdrawing said table means from said grinding edge, said resilient lost motion cam follower terminating transfer of approaching movement from said cam to said table means when said cutting edge abuts said stop means.

4. The combination recited in claim 3, wherein said block is provided with an aperture opening into the cam accommodating opening, and said resilient lost motion cam follower comprises a pin axially shiftable in said aperture and projecting into said opening, said pin having a socket in one end thereof, a threaded adjustable holding member threaded into said aperture, and a helical spring bearing against said holding member and said pin and projecting into said socket for biasing said pin into engagement with the surface of said cam.

5. In a grinding machine for grinding a series of armate concave depressions in the cutting edge of an elongated flat sided blade of a knife or the like, the combination recited in claim 1 wherein said transverse feed means comprises a continuously driven shaft disposed parallel to said grinding wheel axis having a cam thereon disposed in parallelism with the plane of said grinding wheel, and cam follower means depending from said table means into juxtaposition with diametrically opposite faces of said cam to be engaged by said cam for imparting reciprocative approaching and withdrawing movement to said table means relative to said grinding edge, said cam follower means including resilient lost motion means engaged by said cam during approaching movement of said table to terminate transfer of grinding-wheel-approaching movement from said cam to said table means when said cutting edge abuts said stop means and wherein said longitudinal feed means comprises a screw threaded spindle, means interconnecting said spindle with said carriage means for shifting said carriage means in the direction of the axis of said spindle, and means interconnecting said spindle with said driven shaft for intermittently rotating said spindle from said driven shaft.

References Cited in the file of this patent UNITED STATES PATENTS 448,616 Hudson Mar. 17, 1891 1,227,234 Bacon May 22, 1917 1,793,171 Grant Feb. 17, 1931 2,069,140 Freas et a1. Jan. 26, 1937 2,082,832 Hansen June 8, 1937 2,203,530 Kasch June 4, 1940 2,273,456 Zimmerman Feb. 17, 1942 2,510,301 Wiegand June 6, 1950 

